A fiber expansion joint filler should be non-extending, resilient and should not deform, twist or break with ordinary handling. It is composed of cellular fibers securely bonded together and uniformly saturated with asphalt to insure longevity. It should have excellent resiliency and should be unaffected by temperature extremes. A fiber expansion joint filler is ideally suited for joints in sidewalks, driveways, single and multi-level floor slabs and the like, i.e. all areas where expansion and contraction stresses in concrete have to be accommodated to prevent failure. It is particularly suited for highways, municipal streets, airport runways, and similar areas subject to vehicular traffic. Fiber expansion joint fillers are normally produced by cutting an asphalt saturated fiber board into strips of a desired width and length.
Previously, fiber boards to be saturated have been dipped into a solution of asphalt and a solvent, to carry the asphalt and solvent into the fiber board, which is comparatively porous and into which a liquid passes quite readily. Upon removal from the solution, the fiber boards have been taken to a field and placed with spacers between boards so that the solvent could evaporate in the open air, such as in about two weeks or more, depending on the temperature, humidity and winds. There are numerous distinct disadvantages to this procedure. One marked disadvantage is the cost of the solvent, which is all lost to the open air. A second disadvantage is the cost of labor involved in placing the saturated boards individually on spacers for evaporation of the solvent. A third disadvantage is the effect of inclement weather, such as during rainfall and particularly when it is snowing. A fourth disadvantage is pollution of the atmosphere. It is understood that one manufacturer of asphalt saturated fiber board was forced to close its plant in one state, while another operating in another state under a "grandfather clause" was prevented from moving its fiber board saturation operation to a new site where an expanded plant was to be located, because of pollution problems.
In order to recover as much of the solvent as possible, the present applicants and possibly others associated with the assignee of the present application, developed equipment including a tank adapted to be closed so that a vacuum could be pulled on the tank and the pressure reduced to evaporate the solvent from fiber boards placed in the tank, then condensed and the solvent recovered. The fiber boards were placed in a special rack constructed for the purpose and placed in the tank, with the boards therein. The top of the tank was closed, sealed and clamped and then a blend of solvent and asphalt pumped into the tank, then pumped out. Then the pressure within the tank was reduced by a vacuum pump connected in series with a coiled condenser. Some heat was attempted to be applied to the solution remaining on the boards through a few channels welded to the inside of the tank and a heat transfer oil, at 350.degree. to 400.degree. F., passed through the spaces provided by the channels. For the first few minutes, as vacuum was applied, there was a rush of solvent vapor into the condenser, which tended to flood the condenser and, at times, carry over into the vacuum pump and escape into the atmosphere. While a portion of the solvent was recovered, a larger portion remained on or in the boards, so that the expense of placing the boards for drying outdoors and the loss of the solvent evaporated there was not avoided. It was found that it required six days or more to reduce the solvent remaining in the boards to an acceptable amount, i.e. the amount of solvent normally locked in the asphalt or about 6% or less of solvent in proportion to the asphalt.
Among the objects of this invention are to provide a novel method of and apparatus for treating fiber board so as to substantially saturate the boards with asphalt or the like; to provide a method and apparatus which involves a blended solution of solvent and asphalt; to provide such a method and apparatus by which such boards may be subjected to immersion or substantial immersion in such solution, the solution drained and the boards then subjected to vacuum and heat to remove the solvent; to provide such a method and apparatus by which the solvent may be removed by heat and vacuum to a similar extent as though the boards, after the solution is drained from them, were placed individually in the atmosphere for drying for an extended period, as on the order of two weeks or more; to provide such a method and apparatus which recovers substantially all of the solvent, except that which is "locked in" with asphalt; to provide such a method which may be carried out with ease and facility and such apparatus which is particularly adapted to carry out such method; and to provide such method which can be carried out economically and such such apparatus which is economical in operation.